Late Cenozoic sedimentation on the Washington continental slope

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What does this data set describe?

Title: Late Cenozoic sedimentation on the Washington continental slope
Abstract:
The Washington continental slope, which is situated between the continental shelf on the east and Cascadia Basin on the west, consists of an upper and lower slope. The lower slope of borderland is composed of north to northwest trending, en echelon, anticlinal ridges and intervening sediment-filled basins. The indurated mudstone and limestone ridges represent older Cascadia Basin turbidites that have been accreted onto the continental margin within the last two million years as a result of the underthrusting of the Juan de Fuca plate beneath North America. The ridges ages and the borderland structure indicate that deformation has progressed in a westward direction with time and has probably continued up to the present. Folding and thrusting of the outermost or marginal ridges is presently occurring at a rate of 0.7 cm/yr. The depressions between these ridges, which may be filled with hemipelagic and turbidite sediment, often form valleys that drain the submarine canyons notching the upper slope. Since all the borderland ridges are probably less than 2 million years old, the deposition of postdeformational sediment between the ridges must have occurred during the Pleistocene. Approximate Pleistocene sediment accumulation rates range from less than 0.5m/1000 yrs to more than 1m/1000 yrs. Most of this sediment, trapped in the borderland basins, was probably deposited by turbidity currents during periods of glaciation on the adjacent continent. Although deformation of the lower slope has continued throughout the Pleistocene, there is no evidence in the seismic reflection profiles that the major routes of sediment dispersal have shifted significantly since the beginning of postdeformational sedimentation. The sediment in the borderland piston cores consists of interlayer turbidite and hemipelagic deposits. The sediment is divided into glacial and postglacial sections based on a change from foraminiferan-rich, gray lutite to radiolarian-rich, olive gray lutite. This faunal change, which begins at about 10,500 yrs B.P. on the lower slope, is time transgressive in the northeast Pacific and may separate geologic-climate units. It cannot be used to define the Pleistocene-Holocene time-stratigraphic boundary. The postglacial sediment deposited between 10,500 yrs B.P. and the present can be divided into early and late postglacial sections based on the lowest horizon of Mazama glass deposited about 6,750 yrs. B.P. During the last glacial period turbidity currents played a major role in deposition of sediments. The lower continental slope was apparently deluged with turbidity currents enroute to the deep-sea fans of Cascadia Basin. All the canyons notching the upper slope were probably active until about 10,500 yrs. B.P. With the onset of postglacial conditions the importance of hemipelagic sedimentation increased. All the canyons were probably less active and turbidity currents apparently occurred less frequently, were composed of finer grained material, and tended to be depositional in nature. Over the last 6,750 years Astoria, Grays, and Juan de Fuca Canyons have been filling up with hemipelagic mud and some sand/silt turbidites. Willapa Canyon remained an active avenue for nondepositional or erosional turbidity currents until about 5,000 yrs B.P. when it too began to fill up. All these canyons presently appear to be filling up with fine-grained material, which is probably derived primarily from the Columbia River. Quinault Canyon apparently acts as a funnel for a large amount of material that is moving northward along the continental shelf. This material accumulates in the head of the canyon for about 500 years before it is flushed down the canyon as a large turbidity current that flows down lower Quinault Canyon, out lower Willapa Canyon and into Cascadia Basin.
Supplemental_Information:
Seismic reflection profiles, cores, and dredge hauls used in this study were collected on the R/V T. Washington (Scripps Institution of Oceanography) Leg 9A-Seven Tow expedition, and on R/V T.G. Thompson (University of Washington) cruises TT-053, TT-063, and TT-068. Data digitized by the USGS for inclusion into usSEABED (<http://walrus.wr.usgs.gov/usseabed>)
  1. How should this data set be cited?

    Barnard, William Dana , 1973, Late Cenozoic sedimentation on the Washington continental slope: University of Washington, Seattle, WA.

    Other_Citation_Details:
    PhD. dissertation, Department of Oceanography Research supported by the National Science Foundation, Texaco Fellowship in Oceanography, and the U.S. Atomic Energy Commission, Contract AT (45-1)-2225-T24

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -126.41833
    East_Bounding_Coordinate: -124.67000
    North_Bounding_Coordinate: 48.20500
    South_Bounding_Coordinate: 46.04667

  3. What does it look like?

    Barnard_PhD_1973 (JPG)
    Screen grab of GIS-produced sample distribution, with bathymetry and land for reference.

  4. Does the data set describe conditions during a particular time period?

    Calendar_Date: 1973
    Currentness_Reference: Publication date

  5. What is the general form of this data set?

    Geospatial_Data_Presentation_Form: Paper

  6. How does the data set represent geographic features?

    1. How are geographic features stored in the data set?

      This is a Vector data set. It contains the following vector data types (SDTS terminology):

      • Point (72)

    2. What coordinate system is used to represent geographic features?

      Horizontal positions are specified in geographic coordinates, that is, latitude and longitude. Latitudes are given to the nearest 0.00167. Longitudes are given to the nearest 0.00167. Latitude and longitude values are specified in Decimal degrees.

  7. How does the data set describe geographic features?

    Point
    SDTS point (Source: Source report)

    Sample number
    Sample number based on cruise number and sample number (Source: Source report)

    Alpha numeric number based on cruise and core information

    Depth in core
    Subsample depth (Source: Source report)

    Range of values
    Minimum:0
    Maximum:5.22
    Units:Meters
    Resolution:0.01

    Core description
    Core description (Source: Source report)

    Lithologic description of cores and dredges, including color

    Sand
    Qualitative estimate of sand in subsample (Source: Source report)

    ValueDefinition
    AAbundant (>35%)
    CCommon (10-35%)
    ARare (1-10%)
    ATrace (<1%)

    Silt
    Qualitative estimate of silt in subsample (Source: Source report)

    ValueDefinition
    AAbundant (>35%)
    CCommon (10-35%)
    ARare (1-10%)
    ATrace (<1%)

    Clay
    Qualitative estimate of clay in subsample (Source: Source report)

    ValueDefinition
    AAbundant (>35%)
    CCommon (10-35%)
    ARare (1-10%)
    ATrace (<1%)

    Forams
    Qualitative estimate of foraminifera in subsample (Source: Source report)

    ValueDefinition
    AAbundant (>35%)
    CCommon (10-35%)
    ARare (1-10%)
    ATrace (<1%)

    Rads/Diatoms
    Qualitative estimate of radiolaria and diatoms in subsample (Source: Source report)

    ValueDefinition
    AAbundant (>35%)
    CCommon (10-35%)
    ARare (1-10%)
    ATrace (<1%)

    Wood/plant fragments
    Qualitative estimate of wood and plant fragments in subsample (Source: Source report)

    ValueDefinition
    AAbundant (>35%)
    CCommon (10-35%)
    ARare (1-10%)
    ATrace (<1%)

    Dark minerals
    Qualitative estimate of dark minerals in subsample (Source: Source report)

    ValueDefinition
    AAbundant (>35%)
    CCommon (10-35%)
    ARare (1-10%)
    ATrace (<1%)

    Light minerals
    Qualitative estimate of light minerals in subsample (Source: Source report)

    ValueDefinition
    AAbundant (>35%)
    CCommon (10-35%)
    ARare (1-10%)
    ATrace (<1%)

    Volcanic galss
    Qualitative estimate of volcanic glass in subsample (Source: Source report)

    ValueDefinition
    AAbundant (>35%)
    CCommon (10-35%)
    ARare (1-10%)
    ATrace (<1%)

    Planktonic foraminfera
    Ratio of planktonic foraminfera to sum of radiolaria and planktonic foraminifera (Source: Source report)

    Range of values
    Minimum:0
    Maximum:100
    Units:Percent
    Resolution:1.0

    Radiolaria
    Ratio of radiolaria to sum of radiolaria and planktonic foraminifera (Source: Source report)

    Range of values
    Minimum:0
    Maximum:100
    Units:Percent
    Resolution:1.0

    Bulk density
    Bulk density of subsample (Source: Source report)

    Range of values
    Minimum:2.55
    Maximum:2.87
    Units:G/cc
    Resolution:0.01

    Water content
    Average water content (Source: Source report)

    Range of values
    Minimum:21.8
    Maximum:66.2
    Units:Percent
    Resolution:0.01

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)

  2. Who also contributed to the data set?

    William Dana Barnard at the University of Washington for the collection and analysis of data. For inclusion into usSEABED: Digitization: Jennifer Mendonca, (USGS); Formatting corrections: Jane Reid (USGS) and Chris Jenkins (University of Colorado)

  3. To whom should users address questions about the data?

    University of Washington
    P.O. Box 357940
    Seattle, WA 98195

    206-543-5060 (voice)

Why was the data set created?

The recent development of seismic reflection profiling has greatly advanced our knowledge of continental margin structures, while improvements in coring and bottom sampling techniques have made detailed studies of the near-surface sediments more feasible. This study is oriented towards the utilization of these techniques to describe the stratigraphy and near-surface sedimentary record on the Washington continental slope. It is hoped that a better understanding of the late Cenozoic history and development of this region can be gained by integrating data from both seismic profiles and near-surface sediment samples.

How was the data set created?

  1. From what previous works were the data drawn?

  2. How were the data generated, processed, and modified?

    Date: Unknown (process 1 of 1)
    "All cores used in this study were split lengthwise and logged visually. The Rock Color Chart (Geological Society of America, 1963) was used in logging the sediment color. General sediment texture and composition were qualitatively determined by means of smear slides...estimates of texture were made by comparing the sample slides with "standard" sand, silt, and clay slides. This method of estimating sediment composition, although very qualitative, does give a general idea of the sediment components and their relative amounts. All the estimates are based on visual estimates without regard to weight or volume percentages. Bulk densities were measured in a Beckman air comparison pycnometer (model 930); the density was calculated by dividing the weight by the volume. The velocity of sound was measured at 10 cm intervals on an Underwater Systems Sediment Velocimeter (model U.S.I. 103)." For usSEABED, core descriptions were transcribed from drawings using the legends provided. Qualitative estimates of sand, silt, clay abundances were translated using the legends provided, i.e., >35% = abundant, 10-35% = common, 1-10% = rare, and >1% = trace, and mined as a written description.

    Person who carried out this activity:

    University of Washington
    P.O. Box 357940
    Seattle, WA 98195

    206-543-5060 (voice)

    Data sources used in this process:
    • Geological Society of America, 1963

    Data sources produced in this process:

    • Barnard_PhD_1973

  3. What similar or related data should the user be aware of?

How reliable are the data; what problems remain in the data set?

  1. How well have the observations been checked?

    No estimate made for the accuracy of the data in the original report. Data digitized by the USGS and partners were visually compared to the source data, and corrected. Where appropriate, data were tested for completeness using MS Excel. Locations checked using GIS.

  2. How accurate are the geographic locations?

    Navigation by satellite. Latitudes and longitudes given in degrees, tenths, minutes.

  3. How accurate are the heights or depths?

    Water depth determinations by 12-kHz transducer using an assumed sound velocity of 1463 m/sec. No slope corrections were made. Water depths given in meters.

  4. Where are the gaps in the data? What is missing?

    Sample number, station locations, water depth, sampler type, and core length (Appendix 2), core descriptions (Appendix 3); Sediment composition (Appendix 4); microfossil data from piston cores (Appendix 5), and sediment densities and water content(Appendix 8) completely digitized. Microfossil data from dredge haul samples (Appendix 6), carbon values (Appendix 7), and sediment velocities (Appendix 9) were not digitized and are not included in usSEABED.

  5. How consistent are the relationships among the observations, including topology?

    Data fall within normal ranges for the given parameters.

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?

Access_Constraints:
Dissertation is available at libraries and the University of Washington
Use_Constraints:
Cite William D. Barnard and the University of Washington as originators of the data.

  1. Who distributes the data set? (Distributor 1 of 1)

    University of Washington
    P.O. Box 357940
    Seattle, WA 98195

    206-543-5060 (voice)

  2. What's the catalog number I need to order this data set?

    Barnard_PhD_1973

  3. What legal disclaimers am I supposed to read?

    Although this dataset has been used by the USGS, no warranty, expressed or implied, is made by the USGS as to the accuracy of the data. Users of the data should be aware of limitations of the data due to possible imprecision due to navigational inaccuracies and limitations of the statistical data.

  4. How can I download or order the data?

  5. What hardware or software do I need in order to use the data set?

    None

Who wrote the metadata?

Dates:
Last modified: 2005
Metadata author:
U.S. Geological Survey
c/o Jane A. Reid
Geologist
400 Natural Bridges Drive
Santa Cruz, CA 95060

831-427-4727 (voice)
jareid@usgs.gov

Contact_Instructions: Email preferred
Metadata standard:
CSDGM Version 2 (FGDC-STD-001-1998)

Generated by mp version 2.8.17 on Tue May 16 19:56:41 2006